A 42-year-old woman with acute myeloid leukemia undergoing intensive chemotherapy (absolute neutrophil count 80/μL) presents with persistent fever unresponsive to broad-spectrum antibiotics for 7 days. She develops a new productive cough with hemoptysis and pleuritic chest pain. Chest X-ray shows a wedge-shaped consolidation with a surrounding halo of ground-glass opacity. High-resolution CT confirms the halo sign. Sputum culture grows Aspergillus fumigatus. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Invasive Pulmonary Aspergillosis **Key Point:** The combination of severe neutropenia, fever unresponsive to antibiotics, hemoptysis, and the pathognomonic **halo sign** (wedge-shaped consolidation with surrounding ground-glass opacity) on HRCT is diagnostic for invasive pulmonary aspergillosis (IPA). ## Halo Sign: Pathophysiology ```mermaid flowchart TD A[Aspergillus fumigatus spore inhalation]:::outcome --> B[Angioinvasion of pulmonary vessels]:::action B --> C[Vascular thrombosis & hemorrhage]:::action C --> D[Ground-glass opacity around nodule]:::outcome D --> E[Halo Sign on HRCT]:::outcome E --> F[Indicates acute angioinvasive disease]:::outcome ``` **Clinical Pearl:** The halo sign represents pulmonary hemorrhage surrounding a nodule of fungal invasion. It is highly specific for IPA in the setting of severe immunosuppression and indicates angioinvasion — a hallmark of invasive aspergillosis. ## Risk Stratification for IPA | Risk Factor | Presence in This Case | |-------------|----------------------| | **Severe neutropenia** (ANC < 500/μL) | Yes (80/μL) | | **Prolonged neutropenia** (> 7 days) | Yes | | **Hematologic malignancy** | Yes (AML) | | **Recent chemotherapy** | Yes | | **Fever unresponsive to antibiotics** | Yes (7 days) | | **Hemoptysis** | Yes | | **Halo sign on HRCT** | Yes | **High-Yield:** IPA occurs almost exclusively in severely immunocompromised hosts (ANC < 500/μL). Aspergillus fumigatus is the most common causative species; it is ubiquitous in the environment and spreads via airborne spores. ## Angioinvasion: The Defining Feature 1. **Spore inhalation** → alveolar colonization 2. **Hyphal invasion** → pulmonary vessel wall penetration 3. **Thrombosis** → tissue ischemia and infarction 4. **Hemorrhage** → hemoptysis and halo sign 5. **Dissemination** → sinuses, brain, skin if untreated **Warning:** Hemoptysis in a neutropenic patient with fever and pulmonary infiltrates is IPA until proven otherwise. This is a medical emergency. ## Diagnostic Criteria (EORTC/MSG 2020) **Key Point:** Diagnosis requires: - Host factors (severe immunosuppression) ✓ - Clinical features (fever, cough, hemoptysis) ✓ - Radiologic findings (halo sign) ✓ - Mycologic evidence (Aspergillus fumigatus from sputum) ✓ ## Management - **First-line:** IV voriconazole (loading 6 mg/kg IV Q12H × 2 doses, then 4 mg/kg IV Q12H) - **Alternative:** Liposomal amphotericin B (if voriconazole contraindicated) - **Supportive:** Granulocyte colony-stimulating factor (G-CSF) to accelerate neutrophil recovery - **Surgical:** Consider resection of cavitary lesions if accessible and patient stable **Clinical Pearl:** Voriconazole is superior to amphotericin B for IPA in terms of response rates and survival. Posaconazole is an alternative for maintenance therapy. [cite:Harrison 21e Ch 219; Robbins 10e Ch 8]